Instead of using vertices, you can just use the width and height. What you'll have to do is implement: `getFarthestHullPoint()`, and `getFarthestCorePoint()` like in the other geometries.

# getFarthestHullPoint

Assume all coordinates are relative to the rectangle centroid (IE: in the body frame).
This should take a direction vector then it should calculate the location (in that frame of reference) of the point on the perimeter (hull) if you traveled in a straight line from the centroid in the provided direction. The result should be returned/set just like it is in the other geometries.

Here's a rough sketch of what I'm talking about: http://screencast.com/t/IkvmzpdSZS

# getFarthestCorePoint

This does the same but shrinks the shape by subtracting "margin" from it. Return the position of the point on the "core" shape.

Check out the implementation in the circle geometry (easy). Then glance at the polygon geometry if you want... but don't worry about it too much... the rectangle one should be much simpler.

If you need to use vectors to help the math... use a scratchpad. :)